1. Field
The present invention relates to a cutting apparatus for joint cutting system with robot. In detail, a sleeve and a sleeve base are so separable that it is possible to reinforce the strength of the sleeve, which retrains the bending force to the sleeve, though the diameter of the sleeve is minimized. Therefore, the durability of the sleeve is increased and the tough and damage to the bone, the muscle and the skin tissue around the surgical site are decreased owing to the decrease of the diameter of the sleeve. Also when the sleeve is bended the sleeve alone is so changeable that the maintenance cost is reduced and the maintainability is improved. In addition, the machinability of the bone is improved and it is so needless to change the cutter during the surgery that the surgery can be performed rapidly, exactly, and safely.
2. Description of the Related Art
The number of patient with joint disease comprising arthritis, osteoporotic fracture and etc. has been sharply increased as an aged population has been increased owing to the long average life span of human being.
The joint disease in early stage would be cured with non-surgery treatment comprising medication, physical therapy and so on, but the severe joint disease should be performed a surgery on.
Surgery treatment includes arthroscopic surgery, chondrocyte implantation and artificial joint surgery for the severe disease and etc.
The artificial joint surgery is performed in a way that the cutter of the cutting apparatus equipped in the end of variable-positioned arm of a robot rotates with cutting the knee joint according to the information from a computer, and then an artificial knee joint is put in (refer to FIG. 2).
FIG. 1 represents an existing cutting apparatus of joint cutting system with robot, and FIG. 2 represents roughly an artificial joint which is performed with on the knee joint. As depicted, a head 110 is 7.8 mm in a diameter and has a cutter on outer surface and front end surface formed at one end of the position-variable arm of the robot. A shaft 120 which is a hollow bar of 2.3 mm in a diameter is extended from head 110 and the back end of the shaft 120 is connected with a motor (M) equipped at the other end of the position-variable arm of the robot.
And outer circumferential surface of the shaft 120 is supported by a sleeve 130 fixed by the housing of the motor (M) such that the shaft 120 is rotatable. So the rotation of shaft 120 doesn't make any trembling and bending. The cutting is performed by the rotation of the head 110 which is protruded out from the sleeve 130.
The cutting apparatus of FIG. 1 has some drawbacks that the diameter of the head 110 is so large, as mentioned above, around 7.8 mm that it might touch skin tissue during an operation. And therefore the skin and the flesh are to be inevitably cut. Also a surgery to control the cutting path such like a tunnel cutting is not available. Also intense rolling friction between shaft 120 and sleeve 130 would abrade the surfaces after long-term using and make the unordinary rotations.
FIG. 3 shows other example of existing cutting apparatus of joint cutting system with robot which is disclosed in Korean registered patent No. 10-0873014.
Referring to FIG. 3, the joint cutting apparatus has a position-variable arm, a motor (M) at the front end of the arm, a sleeve 14 combined at housing of the motor, and a cutter 10 connected with a shaft of the motor to be rotatable in the sleeve. The cutter 10 comprises a shaft 11 of a hollow bar of cantilever type which is connected with the motor to be rotatable in the sleeve 14 and extended outward the sleeve, and a head 12 formed at the front end of the shaft 11. The cantilever length of the shaft 11 and the diameter of the head 12 are chosen as one of each 20-30 mm and 1.5-4.0 mm, or each 70-80 mm and 4.0-6.0 mm in order that the head 12 bores a hole into the bone.
As stated above, the cutting apparatus in FIG. 3 works with tunneling-like cutting method using cutter with minimal diameter and optimized cantilever length so that the bone would be cut safely and fast, and damage to the bone would be lessen, advantageously. But the shaft 11 is not supported by the sleeve 14 and has cantilever structure which cause disadvantageously trembling and bending. Especially, as the shaft 11 would be rotated over 60,000 rpm during an operation, there would be some drawbacks such like the breakdown of the shaft 11, unsafety and so on. Also, the trembling of the shaft 11 limits to the length of the protrusion in the cantilever structure so that it would be not available in deep surgical site.
Recently, in order to supplement the drawbacks of the cutting apparatus in FIG. 1 and FIG. 3, the diameter of the sleeve is decreased so that tough and damage to the bone, muscle, and skin tissue are lessened, and a cutter support member having multiple bearings in the sleeve has been developed.
However, the cutter support member of this type where the sleeve in the form a hollow bar and the sleeve base in the form of a cap are an integral unit has some defects such like difficult manufacturing, high manufacturing cost, long manufacturing. Especially, the integration of the sleeve and the sleeve base make it difficult to insert a tool into the inner hole of the sleeve or to form the settling groove of bearings on the inner surface of the sleeve so that the bearings should be inserted without the settling groove. Therefore, the diameter of the sleeve could not be decreased and the large diameter would make touch and damage to the bone, muscle, skin tissue around surgical site.
Besides, when the bearings inside the sleeve get damaged owing to the high speed rotation of the shaft of the cutter over 60,000 rpm or the sleeve gets bended by the bending force owing to the movement of the cutting head during the surgery, the sleeve base with the broken-down sleeve should be replaced with new integral unit so that the maintenance cost would be very high, disadvantageously.
Meanwhile, in the said existing cutting apparatuses one of the cutting heads of 7.8 mm and 2.3 mm in diameter is optionally used depending on the process and the cutting head should be changed properly during the surgery which is inconvenient to the operator and increases the surgery time. In other words, the cutting head of 7.8 mm in diameter is used in cutting the surface of the knee joint bone (ex, femur, tibia) on which the artificial joint is settled, and the cutting head of 2.3 mm in diameter is used in drilling the inserting hole (peg, hole in the knee joint bone), in which a fixing protrusion (a2) of the artificial joint (a) is inserted, after inconveniently changing the cutting head of 7.8 mm in diameter.